<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>clearfix</title>
    <style>
        /*第一遍理解记忆：2023-1-18*/
        .box1{
            width:200px;
            height:200px;
            background-color: aqua;
        }
        /*解决外边距重叠*/
        /* .box1::before{
            content:'';
            display: table;
            
        } */
        /*解决高度塌陷*/
        /* .box1::after{
            content:'';
            display:table;
            clear:both;
        } */
        /*多功能类：即可解决高度塌陷，又可解决外边距重叠（记住即可）*/
        .clearfix::before,
        .clearfix::after{
            content:'';
            display: table;
            clear:both;
        }
        .box2{
            width:100px;
            height:100px;
            background-color: chartreuse;
            margin-top:100px;
        }
    </style>
</head>
<body>
    <div class="box1 clearfix">
        <div class="box2"></div>
    </div>
</body>
</html>